The paper presents one of the methods for the development of carbonate reservoirs of TATNEFT’s oil fields associated with low expected oil recovery. This method enables higher recovery factors and provides for infill drilling. The critical factor for drilling infill wells is economic viability, which depends on the costs of construction, completion and operation of infill wells, as well as the resultant oil production rates.
Tatneft has adopted a program of infill drilling targeting several low-productivity carbonate reservoirs. To improve the performance of infill drilling, a decision has been made to use such technologies as slim hole drilling, dual completion technology for simultaneous production from multiple intervals, application of sucker rod pump units for lifting wellstream through production casing (without the use of tubing) and others. One of the objectives of infill drilling program is reduction of well construction costs by means of slim hole drilling (102 and 114-mm). For operation of slim holes, a dual completion system has been designed enabling commingled production from several production zones. This system is based on single-tubing-string dual completion approach extensively used in Tatneft. Dual completion system with segregated lift of production fluids has also been developed for slim holes. This system enables determination of production rates and water cut of each production zone. Production fluid from one production zone is lifted to the surface through the tubing string while fluids from the other zone flow through production string. For the above production casing sizes simple and cost-effective packer elements have been developed. These are sleeve nipples and cup packer.
The systems described in this article have proved efficient and have been recommended for implementation at Tatneft’s fields.
References
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